Romney told Fox News on Tuesday that Gingrich isn't as likely to beat President Barack Obama, and Romney says he has credibility when it comes to understanding the economy.

Throughout the campaign, Romney has emphasized his business experience over his political tenure as governor of Massachusetts.

Romney has rarely had such harsh words for any of his many Republican rivals, largely choosing instead to attack President Barack Obama, stay above the primary fray and frame himself instead as the likely nominee.

His pointed criticism of Gingrich illustrates how seriously he is taking Gingrich's recent rise as his main opponent.